(A) Extraction of the Kerogen from Oil Shale
A wide range of processes involving different kinds of treatments and processing steps for extracting the kerogen trapped in oil shale have been disclosed in the patent and the technical literature. The search for ways of releasing the trapped kerogen has been extensive because there has been a long felt need to economically extract the shale oil from this plentiful source of fuel. There are basically two ways of extracting the shale oil in order to treat it. It can be done by applying the treatment while the oil shale is underground, i.e. in situ type of treatment or it can be mined and brought to a treating site.
Typically the prior art which is directed to the in situ type of treatment involves the injection of hot fluids, usually 200.degree. C., into the oil shale beds to extract the kerogen. The hot fluids disclosed are variously steam, hot water, organic solvents, organic acids or inorganic acids.
In the case where the oil shale is mined, the usual treatment has been to retort the material distilling the volatile hydrocarbons and collecting the distillate. Such a process is described in U.S. Pat. No. 2,694,035 by Lloyd B. Smith et al. The process calls for soaking the oil shale in hydrogen containing gas at 343.degree. C. to 399.degree. C., the addition of small amounts (4.4-22 kgs. per 4400 kgs. of shale) of inorganic polar compounds such as water, sodium hydroxide, calcium chloride to increase the yield and/or the quality of the oil and then subjecting the mixture to the retorting step.
These known techniques suffer from a number of deficiencies such as the inability to recover at least 80 to 85% of the available kerogen bound up in the oil shale. The retort technique has been successful but the amount of shale oil that can be recovered from the available oil shale is in the range of 70% to 80% due to the conversion to gases and unusable coke that results from pyrolysis of oil bearing shale. Another significant deficiency is that the heretofore known retorting technique is uneconomical when processing oil shale that has less than 25 gallons per ton ("GPT") of shale oil. It is uneconomical in terms of heat requirement in that a large amount of heat input is necessary to bring the mineral matrix plus kerogen up to the proper temperature in order to pyrolyze the kerogen. Accordingly, retorting oil shale that has less than 25% kerogen becomes rather costly in terms of the amount of shale oil retrieved versus the heat input. Further, the retort equipment must be quite large in order to accommodate sufficient tonnage of oil shale to produce several hundred gallons of shale oil per retort cycle. Still, the vast majority of oil shale deposits are well below the 25 GPT level.
Thus, what is needed is a technique to extract kerogen which is essentially shale free, from the oil shale rock. This would have a number of advantages. The size of the retort required to pyrolyze shale free kerogen would be decreased anywhere from 50% to 90% and losses due to the need for heating vast amounts of inert and even endothermically reactive shale would be eliminated. Another advantage would be the opportunity to flash pyrolyze the kerogen. Because of the absence of the high heat capacity rock pyrolysis could be accomplished in 1-5 minutes compared to the 30 minutes to 1 hour required by current retorting techniques. It can be expected that there will be an advantage in terms of increasing the yield of oil per unit weight kerogen in the oil shale from 70-80% of conventional retorting of unbeneficiated oil shale to 90% because secondary cracking reactions will not take place in the absence of shale rock.
(B) Upgrading of Fossil Fuels
Techniques are well known for upgrading fossil fuels particularly coal, which have a high sulfur content and high level of incombustible mineral matter (high ash). The use of fused caustic, as one technique to remove sulfur, is disclosed in the work of Robert A. Meyers, one of the co-inventors of this invention, in Chapter 8 of the book entitled: Coal Desulfurization, published in 1977 by Marcel Dekker Inc. of New York, N.Y. Other discussions in Meyers' book deal with the removal of both sulfur and ash by treating the coal with dilute aqueous solutions of mixed caustics under heat and pressure followed by leaching out the hydrolyzed mineral matter with dilute sulfuric acid. The term "fused Caustic" as used herein means that the caustic is in a liquid state.
The former treatments remove little of the ash while the latter utilize costly pressurized equipment. Such equipment is particularly undesirable in processing coal since the processed coal can compete only if it is sold as a relatively low cost fuel. Due to the utilization of caustic solutions in the prior art methods, the pressure equipment must be made of heavy gauge nickel which is a costly construction material, thus rendering these prior art methods uneconomical.